<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Promise封装AJAX</title>
</head>
<body>
<h1>Promise封装AJAX</h1>
<hr>
<button>使用回调函数发送AJAX</button>


<script>
  //接口地址 https://api.apiopen.top/getJoke
  //获取元素对象
  const btn=document.querySelector('button')


  //旧方案
  btn.addEventListener('click',function (){
    //创建对象
    const xhr=new XMLHttpRequest()
    //初始化
    xhr.open('GET',' https://api.apiopen.top/getJoke')
    //发送
    xhr.send()
    //绑定事件，处理响应结果
    xhr.onreadystatechange=function () {
      if (xhr.readyState === 4){
        if (xhr.status>=200&&xhr.status<300){
          console.log(xhr.response.toString())
        }else{
          console.log(xhr.status)
        }
      }
    }
  })
</script>
</body>
</html>